U.S. patent application number 13/032476 was filed with the patent office on 2011-06-16 for method for insert molding bendable position-retaining tubing.
This patent application is currently assigned to MERCURY PLASTICS, INC.. Invention is credited to Grandin Rushlander, Richard T. Seman.
Application Number | 20110139288 13/032476 |
Document ID | / |
Family ID | 38172038 |
Filed Date | 2011-06-16 |
United States Patent
Application |
20110139288 |
Kind Code |
A1 |
Rushlander; Grandin ; et
al. |
June 16, 2011 |
METHOD FOR INSERT MOLDING BENDABLE POSITION-RETAINING TUBING
Abstract
A hollow conduit and process for manufacturing therefor which
includes steps of extruding a first polymer conduit; cutting said
conduit to a pre-determined length; inserting said length into a
split mold having a cavity defined therein; inserting at least one
flexible position retaining means into said mold; injection molding
at least one overmolded polymer onto said plastic conduit and at
least partially onto said position retaining means to form a
position retaining tube, wherein a portion of the length of said
position retaining means is completely embedded within said
overmolded polymer and a portion of the length is not embedded
within said overmolded polymer; and opening said mold and removing
said position retaining tube.
Inventors: |
Rushlander; Grandin;
(Mantua, OH) ; Seman; Richard T.; (Newbury,
OH) |
Assignee: |
MERCURY PLASTICS, INC.
Middlefield
OH
|
Family ID: |
38172038 |
Appl. No.: |
13/032476 |
Filed: |
February 22, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11379450 |
Apr 20, 2006 |
7891382 |
|
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13032476 |
|
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60597667 |
Dec 16, 2005 |
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Current U.S.
Class: |
138/137 ;
264/277 |
Current CPC
Class: |
F16L 11/115 20130101;
F16L 11/08 20130101; F16L 11/112 20130101 |
Class at
Publication: |
138/137 ;
264/277 |
International
Class: |
F16L 11/00 20060101
F16L011/00; B29C 45/14 20060101 B29C045/14 |
Claims
1. A process which comprises: extruding a first polymer conduit;
cutting said conduit to a pre-determined length; inserting said
length into a split mold having a cavity defined therein; inserting
at least one flexible position retaining means into said mold;
injection molding at least one overmolded polymer onto said plastic
conduit and at least partially onto said position retaining means
to form a position retaining tube, wherein a portion of the length
of said position retaining means is completely embedded within said
overmolded polymer and a portion of the length is not embedded
within said overmolded polymer; opening said mold and removing said
position retaining tube.
2. The process of claim 1 wherein said flexible position retaining
means is a metallic wire.
3. The process of claim 2 wherein said first polymer conduit is a
thermoset; and said overmolded polymer is a thermoplastic.
4. The process of claim 1 wherein said cavity in said mold is
corrugated.
5. The process in claim 1 wherein said flexible position retaining
means is at least partially inserted into said mold
6. The process in claim 1 wherein said first polymer conduit is
n-sided where n is greater than or equal to three.
7. The process in claim 1 wherein said position retaining tube is
an n-sided conduit where n is greater than or equal to three.
8. A process which comprises: extruding a first polymer conduit;
cutting said conduit to a pre-determined length; inserting at least
one flexible position retaining means into a split mold having a
cavity defined therein; injection molding at least one overmolded
polymer at least partially onto said position retaining means to
form a position retaining tube, wherein a portion of the length of
said position retaining means is completely embedded within said
overmolded polymer and a portion of the length is not embedded
within said overmolded polymer; opening said mold and removing said
position retaining tube; and positioning said position retaining
tube at least partially around said length of said first polymer
conduit.
9. The process of claim 8 wherein said flexible position retaining
means is a metallic wire.
10. The process of claim 9 wherein said first polymer conduit is a
thermoset; and said overmolded polymer is a thermoplastic
11. The process of claim 8 wherein said cavity in said mold is
corrugated.
12. The process in claim 8 wherein said flexible position retaining
means is at least partially inserted into said mold.
13. The process in claim 8 wherein said first polymer conduit is
n-sided where n is greater than or equal to three.
14. The process in claim 8 wherein said position retaining tube is
an n-sided conduit where n is greater than or equal to three.
15. A hollow conduit which comprises: a polymer inner conduit
having a pair of opposed ends and an interior and an exterior
surface; an overmolded polymer forming a plurality of retaining
portions along at least a portion said conduit between said ends
bonded to said inner conduit about at least a portion of said
exterior surface of said inner conduit; and said overmolded polymer
having at least one flexible position retaining means having a
length, wherein a portion of the length is completely embedded
within said retaining portions of said overmolded polymer and a
portion of the length is not embedded within said overmolded
polymer; and said at least one flexible position retaining means
extending at least partially along a length of said overmolded
polymer.
16. The hollow conduit of claim 15 wherein said flexible position
retaining means is a metallic wire.
17. The hollow conduit of claim 16 wherein said inner conduit is a
thermoset; and said overmolded polymer is a thermoplastic.
18. The hollow conduit of claim 15 which further comprises: at
least two flexible position retaining means, each having a length,
spaced oppositely around the periphery of said hollow tube, each of
said at least two flexible position retaining means having a
portion of its length completely embedded within said overmolded
polymer and a portion of its length not embedded within said
overmolded polymer.
19. The hollow conduit of claim 15 which further comprises: at
least three flexible position retaining means, each having a
length, spaced equidistantly around the periphery of said hollow
tube, each of said at least three flexible position retaining means
having a portion of its length completely embedded within said
overmolded polymer and a portion of its length not embedded within
said overmolded polymer.
20. The hollow conduit of claim 15 which further comprises: at
least two flexible position retaining means, each having a length,
spaced non-equidistantly around the periphery of said hollow tube,
each of said at least two flexible retaining means having a portion
of its length completely embedded within said overmolded polymer
and a portion of its length not embedded within said overmolded
polymer.
Description
CROSS-REFERENCE
[0001] This application claims priority from U.S. patent
application Ser. No. 11/379,450 filed Apr. 20, 2006, which claims
priority from U.S. Provisional Patent Application Ser. No.
60/597,667 filed Dec. 16, 2005.
TECHNICAL FIELD
[0002] The invention relates generally to bendable
position-retaining and/or repositionable yet shape-retaining
tubing. In one embodiment of the invention at least one second
polymer having at least one position retaining means at least
partially embedded therein is molded onto a conduit made of a first
polymer. More particularly, the invention relates to the processing
of a conduit made of a first polymer, such processing involving
injection overmolding of another typically thermoplastic material
with flexible wire at least partially embedded therein to form
flexible, position-retaining as well as repositionable yet shape
retaining tubing.
BACKGROUND OF THE INVENTION
[0003] Thermoplastic tubing is used in a variety of applications,
such as appliance input and output lines, garden hoses, automobile
hoses, medical devices, etc. The tubing is often flexible and able
to bend upon the application of an external force. Typically, upon
the removal of the external pressure the tubing relaxes to its
original position. Attempts have been made to create a tubing
product that will retain a predefined shape, see for example U.S.
Pat. No. 6,455,117 and Canadian Patent 1,229,313. However, to date
no technology has been successful in creating a method to produce
flexible tubing material that retains a nonlinear shape without
impeding the flow of fluids and gases passing therethrough.
[0004] Plastics extrusion processing is defined as converting
plastic powder or granules into a continuous uniform melt and
forcing this melt through a die which yields a desired shape. This
melted material must then be cooled back to its solid state as it
is held in the desired shape, so an end product can be
realized.
[0005] Single screw extruders are the most common in use today.
Extruder diameters range from 1/2'' to 12'' in a barrel inner
diameter. The hopper of an extruder accepts granules or powder
which pass through a vertical opening in the feed section where
they are introduced to a rotating screw with spiral flights. The
material is conveyed along the screw and heated inside the barrel,
with the goal being to reach the die system in a totally melt phase
at an acceptable and homogeneous temperature, and being pumped at a
consistent output rate.
[0006] The barrel is heated and cooled by heater/cooler jackets
surrounding its outer wall to aid in the melting of the material on
the screw. Heater/coolers are electrically heated through heating
elements cast into aluminum, with either cooling tubes also cast
into the aluminum or deep fins cast on the outer surfaces of the
heaters/coolers to allow air cooling of the barrel via blowers.
Temperature of the various barrel zones are set according to the
material, screw design, and processing goals. These barrel zone
temperature settings vary widely, depending on the material used or
the product being made while the control of the temperature at the
deep barrel thermocouple position for a given situation is
typically maintained within a close tolerance range to minimize
variations of material exiting the die system. The screw is the
heart of the extrusion process and designs for which have varied
with time as understanding of the melting process of the plastic
material moving along the screw has increased. Since some materials
tend to trap air as they start to melt, or contain moisture or
volatiles, that will create porosity in the final product, a vent
is typically positioned at a point in the barrel to remove the
porosity by allowing the escape of gases.
[0007] The melt must be shaped and cooled by product sizing and
cooling equipment to its solid phase while forming a product that
falls within given size tolerances. The dies to create the end
products from a melt are varied depending on the shapes involved.
Pipe and tubing are cooled through simple, open water troughs, or
pulled through vacuum sizing tanks, where the melt is held in a
sizing sleeve for a short time in a water filled vacuum chamber.
Custom profiles come in various shapes and are commonly made of
materials that have high melt viscosity, so they are easy to hold
shape while they cool. These products can be cooled by forced air,
water troughs, or water spray methods. The methods of getting the
many shapes include various sizing fixtures to hold the extrudate
as it is pulled through the system and cooled. The material can
also be coextruded, i.e., made with more than one material.
Coextrusion typically requires a dual-extrusion head and multiple
extruders using a specialized die system to bring these layers
together with a common sizing and shaping system. Rates of 100 feet
per minute are routinely achieved.
[0008] To accurately maintain diameter and wall thickness of
polymer tubes, a uniform flow rate of melt from the extruder must
be guaranteed. All extruders, even those designed for producing
extremely tight tolerances will exhibit some surging as a result of
electrical drive control fluctuations, screw design, and the normal
rheological variation in the polymer. Clearly, higher than
commercially acceptable reject rates and waste levels will result
if the process relies solely on extruder stability.
[0009] Injection molding of thermoplastics is a process by which a
polymer is melted and injected into a mold cavity void. The mold
used to create the final part is the inverse shape of the desired
final product. Molds are typically made of hardened steel or
aluminum. Once the melted plastic is injected into the mold, it
cools to a shape that reflects the form of the cavity. The result
is a finished part needing no other work before assembly into or
use as a finished part.
[0010] The injection molding machine has two basic components: an
injection unit to melt and transfer the plastic into the mold; and
a clamp to hold the mold shut against injection pressures and for
parts removal. The injection unit melts the plastic before it is
injected into the mold. It then injects the melt with controlled
pressure and rate into the mold. After the injection cycle, the
clamp gently opens the mold halves so the part can be removed from
the mold.
[0011] Important factors in the processing of plastic for the
injection molding process include temperature, consistency, color
dispersion and density of the melt. Conductive heat supplied by
barrel temperature and mechanical heat generated by screw rotation
both contribute to the processing of good quality melt. Often, most
of the energy available for melting the plastic is supplied by
screw rotation. Mixing happens between screw flights and the screw
rotates, smearing the melted surface from the plastic pellet. This
mixing/shearing action is repeated as the material moves along the
screw until the plastic is completely melted.
[0012] When the polymer is a thermoplastic, injection molding uses
a screw or a plunger to feed the polymer through a heated barrel to
decrease its viscosity, followed by injection into a heated mold.
Once the material fills the mold, it is held under pressure while
chemical crosslinking occurs to make the polymer hard. The cured
part is then ejected from the mold while at the elevated
temperature and cannot be reformed or remelted.
[0013] When thermoplastics are heated in an injection press, they
soften and as pressure is applied, flow from the nozzle of the
press into an injection mold at the injection points. The mold has
cavities that, when filled with the thermoplastic material, define
the molded part. The material enters these cavities through
passages cut into the mold, called runners. The mold also has
passages in it to circulate a coolant, usually water, through
strategic areas to chill the hot plastic. As it cools, the
thermoplastic material hardens. When cooled enough, the mold opens
and the part is removed.
[0014] Injection molding of thermoplastics is increasingly regarded
as the preferred method for delivering high quality, value added
commercial parts. This process allows for high volume production of
complex tightly toleranced three-dimensional parts.
[0015] Insert molding is a type of injection molding process.
Insert molding builds on the technology of injection molding by
placing an insert piece into the cavity of the injection mold
before the melted thermoplastic is injected. As the injected melted
plastic cools, it typically bonds with the insert piece to create a
single object.
[0016] In one embodiment the melted plastic can create molecular or
mechanical bonds with the insert piece, depending on the material
of each. The insert piece can be a thermoplastic or a metal. If the
insert material is the same or very similar to the thermoplastic of
the injected melted plastic a molecular bond will form between the
two. Molecular bonds have strong physical strength, as well as
strong leak resistance. If the insert material and injected plastic
are substantially different, no molecular bond will occur, but
instead a mechanical bond will form by the shrinking of the
injected material as it cools or by bonding of the irregularities
in the surface of the insert by the injected material.
[0017] Standard injection molding presses can be used for insert
molding, but special molding machine designs that are better suited
for insert molding also exist. Specialized insert molding presses
are designed with added features to ease the loading of the insert
pieces into the mold, and to hold the insert pieces in place during
the injection and hardening of the melted polymer.
[0018] The design considerations for insert molding are generally
the same as the considerations for other types of injection
molding, such as the rate of flow of the melted polymer, and the
pressure and temperature of the melted injected polymer. Additional
concerns unique to insert molding usually relate to the bonding
between the insert piece and injection molding material. Examples
of additional concerns are the material of the insert piece, the
pull and compression strength requirements, the leak test
requirements, and the torque or axial force requirements of the
bond between the insert piece and the overmolded second
polymer.
SUMMARY OF THE INVENTION
[0019] To date there has been no effective processing combination
which combines the speed of extrusion with injection molding to
fabricate fluid or gas transporting conduits which retain a
non-linear shape upon the application of an external force which
imparts a bend into the longitudinal axis of the part. In
accordance with this invention, there is disclosed a product made
by a sequence of processing steps in which a flexible,
position-retaining tubing capable of transporting fluid or gases is
manufactured which retains its non-linear shape even when the
applied force is removed.
[0020] The bendable position retaining conduit of the present
invention is generally made by combining the two processing
methodologies: extrusion and injection molding. In one aspect of
the invention extruded profiles are cut to length. The extruded
profile can be of any geometric shape or cross section, and in a
preferred embodiment are circular or generally circular. The
profiles are typically thermoplastics and in a specialized
embodiment are either crosslinked or at least partially crosslinked
using known crosslinking methodologies, a non-limiting list of
crosslinking methodologies including chemical crosslinking and
electron beam crosslinking. The extruded profile is subsequently
positioned in a mold having a cavity of defined geometry, the
cavity including a void for insertion of a position-retaining
means, said means preferably being metallic wire of appropriate
gauge. Upon closure of the mold (preferably of split mold
configuration) a second thermoplastic is injected into the cavity
mold containing the metallic wire. The injected polymer has a more
rubbery characteristic than the extruded profile polymer.
[0021] The Shore durometer, also known as the Rockwell hardness
test, is an instrument used to measure hardness of the polymer.
There are various Shore scales in use today. The Shore A and Shore
D scales are commonly used when referencing hardness of rubbers or
synthetics. The Shore "A" scale ranges from 0 to 100 units, wherein
the lower the Shore A value of a polymer, the softer the polymer,
while the higher the value, the harder the polymer. The Shore "D"
scale is generally used to measure harder plastics and polymers. In
this invention the extruded profile polymer in the final product
will have a higher Shore value than the injection molded polymer.
The Shore values for the extruded profile polymer and the injection
molded polymer used in the final tubing product may have any value
from the Shore A or Shore D scale. In general, the durometer of the
overmolded polymer will be the same as or lower than that of the
extruded polymer. In one embodiment of the invention the difference
in Shore values will be approximately 5%-50% on the same scale,
more preferably 5%-25% on the same scale.
[0022] It is an object of this invention to illustrate a process
which employs insert molding of a second polymer, copolymer, or
polymeric blend with at least one position retaining means,
preferably a wire which has been at least partially inserted or
embedded into the second polymer onto a linear conduit made from a
first polymer, preferably by extrusion, to produce a flexible,
non-linear position-retaining tubing when bent.
[0023] It is another object of this invention to illustrate a
process that allows for at least partial insertion of two or more
position retaining means, preferably wires, in different locations
axially adjacent to the perimeter of the hollow tube, made
preferably by extrusion, as well as in different special
relationships along the longitudinal axis of the hollow tube to
allow the tubing to retain a manually formed position without
relaxing to its original essentially linear position when the
position forming pressure is removed.
[0024] It is a further object of this invention to illustrate a
process for the manufacturing of a flexible, non-linear
position-retaining tubing that does not impede the flow of liquid
or gas through the open volume or void in the center of the
tubing.
[0025] It is another object of this invention to illustrate a
process for the manufacturing of a flexible, non-linear
position-retaining tubing that allows the liquid or gas to flow
without contact with the typically metallic insert wire that allows
the tubing to retain its non-linear shape, minimizing corrosion or
degradation of the typically metallic insert as well as preventing
contamination of the liquid or gas flowing through the tubing.
[0026] It is yet another object of this invention to illustrate a
process for the manufacturing of a flexible, position-retaining
tubing in which a bond is formed between the fluid or gas carrying
inner conduit made of a first polymer and the injection overmolded
second polymer wall that the typically metallic wire is at least
partially embedded therein.
[0027] These and other objects of the present invention will become
more readily apparent from a reading of the following detailed
description taken in conjunction with the accompanying drawings
wherein like reference numerals indicate similar parts, and with
further reference to the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] The invention may take physical form in certain parts and
arrangements of parts, numerous embodiments of which will be
described in detail in the specification and illustrated in the
accompanying drawings which form a part hereof, and wherein:
[0029] FIG. 1 is a side view of a tubing product in a linear
configuration having one metallic wire position retaining means
partially embedded therein;
[0030] FIG. 2 is a side view of FIG. 1 in a nonlinear
configuration;
[0031] FIG. 3 is a side view of another embodiment of a final
tubing product in a linear configuration illustrating two partially
embedded wire position retaining means;
[0032] FIG. 4 is a side view of FIG. 3 in a nonlinear
configuration;
[0033] FIG. 5 is a side view of another embodiment of a final
tubing product in a linear configuration illustrating four
partially embedded wires embedded therein, each wire radially
spaced about the longitudinal axis of the tubing product;
[0034] FIG. 6 is a side view of FIG. 5 in a nonlinear
configuration;
[0035] FIG. 7 is a cross-sectional view of FIG. 6 on the plane 7-7
illustrating consistent wire spacing;
[0036] FIG. 8 is a side view of another embodiment of a final
tubing product in a linear configuration illustrating two partially
embedded wires embedded therein, unequally spaced about the
longitudinal axis of the tubing product;
[0037] FIG. 9 is a side view of FIG. 8 in a nonlinear
configuration;
[0038] FIG. 10 is a cross-sectional view of FIG. 9 on the plane
10-10 illustrating inconsistent wire spacing;
[0039] FIG. 11 is a side view of another embodiment of a final
tubing product in a linear configuration illustrating two wire
position retaining means which only partially extend along the
overmolded polymer at non-opposed locations;
[0040] FIG. 12 is a side view of FIG. 11 in a nonlinear
configuration;
[0041] FIG. 13 is a side view of an alternate embodiment of a final
tubing product in a linear configuration illustrating a
non-circular interior profile of the extruded part;
[0042] FIG. 14 is a side view of FIG. 13 in a nonlinear
configuration;
[0043] FIG. 15 is a cross-sectional view of FIG. 14 on the plane
15-15;
[0044] FIG. 16 is a side view of an alternate embodiment of a final
tubing product in a linear configuration illustrating a
non-circular overmolded polymer;
[0045] FIG. 17 is a side view of FIG. 16 in a nonlinear
configuration;
[0046] FIG. 18 is a cross-sectional view of FIG. 17 on plane
18-18;
[0047] FIG. 19 is a side view of yet another embodiment of a final
tubing product in a linear configuration illustrating inconsistent
corrugation patterns of the overmolded polymer along the length of
the tubing product;
[0048] FIG. 20 is a side view of FIG. 19 in a nonlinear
configuration;
[0049] FIG. 21 is a side view of another embodiment of a final
tubing product in a linear configuration illustrating a mechanical
bond between the interior extruded profile and an overmolded
plastic sleeve;
[0050] FIG. 22 is a side view of FIG. 21 in a nonlinear
configuration; and
[0051] FIG. 23 is a cross-sectional view of FIG. 22 on plane
23-23.
DETAILED DESCRIPTION OF THE INVENTION
[0052] Referring now to the drawings wherein the showings are for
purposes of illustrating numerous embodiments of the invention only
and not for purposes of limiting the same, the figures show tubing
that is bendable and able to retain a manually induced
position.
[0053] FIGS. 1-2 illustrate an embodiment of the invention. FIG. 1
illustrates the tubing 20 in its original, essentially linear,
position before an external bending force has been applied. The
inner essentially linear and cylindrical conduit 22 made of the
first polymer, preferably by extrusion, is attached to the
overmolded second polymer 24 which creates the corrugated external
wall of the final tubing product 20. While the external wall
illustrated in FIG. 1 is corrugated, the invention is not limited
to that geometry. Other shapes and textures are within the scope of
the invention or its equivalents. Flexible wire 26 is at least
partially embedded or inserted into the second overmolded injected
polymer 24, giving the final tubing product the physical
characteristics that allow it to retain a nonlinear shape without
returning to its original position shown by FIG. 1 after the
external pressure is removed. The flexible wire 26 is at least
partially embedded in the exterior overmolded second polymer 24
through a mechanical bond since the wire 26 will typically be
comprised of a metallic material and the overmolding material 24
will be a polymer. Leak resistance of the connection between the
wire 26 and the overmolded second polymer 24 is not essential
because the gas or liquid running through the final tubing product
20 will be confined to inner conduit 22 made of the first polymer,
and therefore will not have contact with the mechanical bonds
between the wire 26 and the exterior overmolded second polymer
24.
[0054] FIG. 2 illustrates the tubing 20 shown in FIG. 1 after an
external manual force F has changed its position to a nonlinear
form. After the removal of the outside force, the tubing retains
the new position and does not relax back to its original position
without a new and separate force again changing its position due to
the incorporation of position retaining means 26 at least partially
embedded in the tubing 20. The tubing has the ability to retain the
nonlinear position due to the position retaining means (preferably
flexible wire 26) that is at least partially embedded in the
overmolded second polymer 24.
[0055] FIGS. 3-4 illustrate another embodiment of the invention.
FIG. 3 illustrates the tubing 20 in its original linear position
before any external force has been applied to change its position.
This embodiment of the invention has a quantity of two (2) flexible
wires 26 and 26a bonded by mechanical bonds and embedded at least
partially within the exterior overmolded second polymer 24 which
surrounds the inner extruded conduit 22. In the figure, the
flexible wires 26 and 26a are positioned approximately 180 degrees
apart from one another radially within the second overmolded
polymer 24. It is not intended by the positioning of the wires in
this figure to imply that the wires cannot be spaced in a different
configuration or at different locations around the perimeter of the
tubing. The insertion of additional flexible wires 26 and 26a into
the overmolded second polymer 24 will increase the strength of the
final tubing product 20 to hold a nonlinear position, without
relaxing back to its original linear position. Adding additional
flexible wires to the injected polymer increases the final tubing
product's strength against inadvertent external forces such as, but
not limited to, vibration or air flow that may otherwise act to
change the position of the tubing from its desired and
predetermined non-linear position.
[0056] FIG. 4 illustrates the tubing 20 shown in FIG. 3 after an
external manual force F has changed its position. The additional
inserted flexible wire 26a will increase the final tubing product's
20 strength to maintain the position brought on by the external
force after the release of that force, and decrease the possibility
that inadvertent forces will change the position of the tubing.
[0057] FIGS. 5-7 show yet another embodiment of the invention. FIG.
5 illustrates the tubing 20 in its original linear position before
any external force has been applied. This embodiment of the
invention has a quantity of four (4) flexible wires 26, 26a, 26b
and 26c (hidden) bonded by mechanical bonds and embedded within the
exterior overmolded second polymer 24. The wires 26, 26a, 26b and
26c are shown in the figure to be positioned at approximately 90
degrees apart from one another radially within the second
overmolded polymer 24 of the final tubing product 20, however it is
acknowledged that the position of the wires 26, 26a, 26b and 26c
does not have to be at consistent or equal intervals, nor at any
predetermined location around the perimeter of the inner conduit 22
of the tubing 20 inserted within the second overmolded polymer 24.
The increase in the quantity of flexible wires 26, 26a, 26b and 26c
will, again, increase the tubing's 20 strength against inadvertent
repositioning by an unintended external force.
[0058] FIG. 6 illustrates the tubing 20 shown in FIG. 5 after an
external manual force F has changed the position of the tubing. The
strength of the tube 20 to resist unintended external forces is
increased by having four embedded flexible wires 26 as opposed to
the fewer flexible wires in the previously shown embodiments.
[0059] FIG. 7 shows a cross section of FIG. 6 taken along the plane
shown in FIG. 6 as PLANE 7-7. The four (4) flexible wires 26, 26a,
26b and 26c are shown embedded and equally spaced within the
overmolded second polymer 24 that was injected onto the cylindrical
inner conduit 22 made of the first polymer.
[0060] FIGS. 8-10 illustrate another embodiment of the invention.
FIG. 8 illustrates the tubing 20 in its original linear position
before any external force has been applied to change its position.
This embodiment of the invention has a quantity of two (2) flexible
wires 26 and 26a bonded by mechanical bonds and embedded at least
partially within the exterior overmolded second polymer 24. In the
figure, the flexible wires 26 and 26a (hidden) are positioned near
one another radially within the second overmolded polymer 24. It is
not intended by the positioning of the wires in this figure to
imply that the wires cannot be spaced in a different configuration
or at different locations around the perimeter of the tubing.
[0061] FIG. 9 illustrates the tubing 20 shown in FIG. 8 after an
external manual force F has changed its position. The additional
inserted flexible wire 26a will increase the final tubing product's
20 strength to maintain the position brought on by the external
force after the release of that force, and decrease the possibility
that inadvertent forces will change the position of the tubing.
[0062] FIG. 10 shows a cross section of FIG. 9 taken along the
plane shown in FIG. 9 as PLANE 10-10. The two (2) flexible wires 26
and 26a are shown embedded and unequally spaced within the
overmolded second polymer 24 that was injected onto the cylindrical
inner conduit 22 made of the first polymer.
[0063] FIG. 11-12 demonstrate a further embodiment of the
invention. FIG. 11 shows the tubing 20 in its original linear
position before any external bending force has been applied to the
tubing. Two pieces of flexible wire 26 and 26a are positioned
approximately 180 degrees apart from one another radially within
the overmolded injected second polymer 24. The flexible wires are
also spatially separated along the longitudinal axis of the tubing
20. This configuration of the wires 26 and 26a in the overmolded
second polymer 24 allow for more than one bend direction to be
created in the tube's 20 positioning, allowing for more flexibility
in the positioning of the tube.
[0064] FIG. 12 shows the tubing 20 shown in FIG. 11 after external
manual forces F1 and F2 have been applied to the tube, changing its
position to a nonlinear form. External forces in opposite
directions F1 and F2 create opposing directional bends in the
tubing 20 creating an S-like shape. The addition of spatially
separate flexible wires 26 and 26a embedded in the overmolded
second polymer 24 allow for many new possibilities in the
positioning of the tubing.
[0065] FIG. 13-15 illustrate yet another embodiment of the
invention. FIG. 13 shows the tubing 28 in its original linear
position before any outside forces have been applied to the tubing,
changed its shape to a nonlinear form. The overmolded second
polymer 24 is injected over the linear, triangular shaped inner
conduit made of the first polymer 30. A flexible wire 26 is
embedded in the injected thermoplastic 24 to give the final tubing
product the physical characteristics to enable it to hold a
position brought on by an external force after the external force
has been removed.
[0066] FIG. 14 shows the tubing 28 shown in FIG. 13 after an
external manual force F has been applied to the tube, changing its
position to a nonlinear form. As shown in previous embodiments,
many variations of quantities and positions of the flexible wires
can alter the form-sustaining properties of the tubing.
[0067] FIG. 15 shows a cross sectional view of FIG. 14 along the
marked PLANE 15-15. The cross sectional view shows the triangular
shaped inner conduit 30 made of the first polymer surrounded by the
overmolded second polymer 24 with the flexible wire 26 embedded in
that overmolded second polymer 24. Though this embodiment
illustrates a triangular shaped inner conduit 30, it is
acknowledged that the inner conduit's shape is not limited to a
cylindrical or triangular shape, and can be any shape that allows
for a hollow cavity through the length of the tubing product and
does not impede the flow of liquid or gas through the inner
conduit.
[0068] FIG. 16-18 illustrate yet another embodiment of the
invention. FIG. 16 shows the tubing 34 in its original linear
position before any outside forces have been applied to the tubing,
changed its shape to a nonlinear form. The overmolded second
polymer 32 is injected into a corrugated triangular shaped mold
over the linear inner conduit made of the first polymer 22. A
flexible wire 26 is embedded in the injected thermoplastic 32 to
give the final tubing product 34 the physical characteristics to
enable it to hold a position brought on by an external force after
the external force has been removed.
[0069] FIG. 17 shows the tubing 34 shown in FIG. 16 after an
external manual force F has been applied to the tube, changing its
position to a nonlinear form. As shown in previous embodiments,
many variations of quantities and positions of the flexible wires
can alter the form-sustaining properties of the tubing.
[0070] FIG. 18 shows a cross sectional view of FIG. 17 along the
marked PLANE 18-18. The cross sectional view shows the inner
conduit made of the first polymer 22 surrounded by the triangular
shaped overmolded second polymer 32 with the flexible wire 26
embedded in that overmolded second polymer 32. Though this
embodiment illustrates a triangular shaped overmolded second
polymer 32, it is acknowledged that neither the inner conduit's
shape or the overmolded second polymer's shape are limited to a
cylindrical or triangular shape, and can be any shape that allows
for a hollow cavity through the length of the tubing product and
does not impede the flow of liquid or gas through the inner
conduit.
[0071] To create the bendable, position-retaining tubing, the
flexible wire(s) are positioned in the desired axial position(s)
around the perimeter of the inner polymer conduit which is made
preferably by extrusion, and are positioned in the desired vertical
location(s) along the longitudinal axis of the inner conduit in the
void cavity of the mold used for the injection molding of the
tubing. The inner conduit made of the first polymer is also
positioned inside the mold cavity to create the interior barrier
wall of the mold for the injection molding of the second polymer
material. In the overmolding process a second plastic is melted and
injected into the mold cavity void, defined in this instance as the
void volume between the mold core body and the outer wall of the
inner conduit. The melted plastic will fill the mold cavity void,
surrounding the flexible wire(s). Once the melted plastic is in the
mold, it cools to a shape that reflects the form of the cavity and
core. For this invention, the mold core body has corrugations on
the wall to create peaks and valleys that appear on the exterior
walls of the overmolded second polymer of the final tubing product.
The distance between and the height of the peaks and valleys of the
corrugation can vary, or be consistent throughout the tubing. There
is no required height or distance between the peaks and valleys of
the corrugation. The resulting part is a finished part needing no
other work before assembly into or use as a finished part.
[0072] FIGS. 19-20 illustrate an additional embodiment of the
invention. FIG. 19 illustrates the tubing 20 in its original linear
position before any outside forces have been applied to the tubing,
changed its shape to a nonlinear form. The overmolded second
polymer 24 is injected over the linear inner conduit made of the
first polymer 22. The overmolded second polymer 24 in this
embodiment has an inconsistent corrugation pattern. Sets of peaks
and valleys are separated by straight expanses of the overmolded
polymer 24 without any corrugations. A flexible wire 26 is embedded
in the injected thermoplastic 24 to give the final tubing product
the physical characteristics to enable it to hold a position
brought on by an external force after the external force has been
removed.
[0073] FIG. 20 shows the tubing 20 shown in FIG. 19 after an
external manual force F has been applied to the tube, changing its
position to a nonlinear form. As shown in previous embodiments,
many variations of quantities and positions of the flexible wires
can alter the form-sustaining properties of the tubing. Many
variations of shapes of the interior conduit 22 and the overmolded
polymer 24 can also be used.
[0074] FIGS. 21-23 show an alternative embodiment of this
invention. FIG. 21 illustrates a final tubing product 36 wherein
the overmolded second polymer 40 is injection molded with a
flexible wire 42 embedded within the overmolded second polymer 40,
with no inner conduit 38 in the center using a mandrel to form the
inner cylindrical wall of the second, exterior polymer 40. The
sheath-like result is then slipped over the inner conduit 38
forming the final tubing product 36.
[0075] FIG. 22 shows the final tubing product 36 of FIG. 21 after
an external force F has altered the original linear position of the
tubing 36 to a non-linear position. When an external force F
changes the position of the cover (comprised of the overmolded
second polymer 40 and the flexible position retaining means 42) and
the inner conduit 38 significantly enough, a mechanical bond would
be created, essentially creating a two-part version of the
bendable, position-retaining tubing product 36. This embodiment
would eliminate the bond between the inner conduit made of the
first polymer 38 and the outer sleeve made of the second polymer 40
and position retaining means 42, allowing more combinations of
materials for the inner conduit 38 and outer sleeve to be realized.
Most thermoplastics and thermosets would be appropriate for use in
both the inner conduit and outer sleeve.
[0076] FIG. 23 shows a cross sectional view of FIG. 22 along the
marked PLANE 23-23. The cross sectional view shows the inner
conduit made of the first polymer 38 surrounded by the overmolded
second polymer 40 with the flexible wire 42 embedded in that
overmolded second polymer 40. Since no chemical bond exists between
the inner conduit 38 and the overmolded second polymer 40 a gap 44
exists between the inner conduit 38 and the overmolded second
polymer 40. This invention does not intend to limit the distance of
the gap between the inner conduit 38 and the overmolded second
polymer 40, however the gap that exists must allow a mechanical
bond to be created between the inner conduit 38 and the overmolded
second polymer 40 when an external force is applied and the
position of the tubing product is altered from its original linear
form to a new nonlinear position.
[0077] One further embodiment of this invention is to utilize
extrusion to attach the inner conduit first polymer and the second
outer polymer to one another. The extrusion process would yield the
same result as the injection molding process by means of running
wire through a cross head with the wire between the layers of the
material, or embedded in one of the materials. Extrusion would be
used to create the inner conduit made of the first polymer which
will ultimately create the inner tube wall of the final tubing
product. Upon exiting the extruder the inner tube would enter a
crosshead die which places continuous lengths of wire from payoff
reels, onto the surface of the first tube. A second extruder would
then be attached to the crosshead die and utilized to extrude the
second polymer material that will become the outer wall of the
final tubing product over both the flexible position retaining
means and the first inner tube previously extruded. An alternative
construction would utilize three material layers, two of which
would be the same material used on the exterior of the final tubing
product, and extruding the three materials at the same time with
the wires embedded between the two identical materials.
[0078] The flexible position retaining means embedded in the
second, outer polymer can be composed of any material that is
flexible enough to achieve the nonlinear position desired for the
final tubing product, and has the physical properties allowing the
final tubing product to retain a nonlinear position. The materials
that can be used to achieve the desired effect of the flexible
position retaining means are well-known within the art. Some
illustrative and non-limiting examples of appropriate material are
copper or aluminum wires, bands, or strips. Other possibilities
include metal or non-metal wires, bands, or strips that have the
proper physical characteristics to flex and retain the position of
the final tubing product.
[0079] While the precise composition of the inner conduit comprised
of the first polymer and overmolded second polymer are not required
to be of any specified polymer, in general, there are several
guidelines which are applicable in the practice of this invention.
It is, of course, recognized that the precise operating conditions
utilized in the overmolding process are well-known in the art and
are specific to each injection molded polymer. It is well within
the skill of the art to determine the applicable conditions which
will result in the appropriate overmolded second polymer and inner
plastic conduit. The plastics used for the inner conduit and
exterior overmolding plastic must have an adequate flexibility for
the purpose in which the final tubing product will be used. The
plastic conduit can be a thermoplastic or a thermoset. The
overmolded second polymer must be capable of forming either a
molecular or mechanical bond with the plastic of the conduit.
[0080] At least one embodiment of this invention will utilize an
inner extruded tube that is made of an at least partially
cross-linked material. The final percentage of cross-linking will
be dependent on the final use application of the product. This
embodiment will have a preferred cross-linking of at least 25%,
more preferably of 50% and most preferably of at least 70-75%.
Applications that require an odorless and tasteless means of
transporting fluids will require the highest percentage of
cross-linking of the material of the inner conduit.
[0081] In the practice of this invention, illustrative and
non-limiting examples of the polymers which may be used in various
combinations to form the plastic conduit as well as polymers which
may be used in the overmolding process would include: nylons or
polyamides, including various types of nylon-6, nylon-6/6,
nylon-6/9, nylon-6/10, nylon-6/12, nylon-11, nylon-12; polyolefin
homopolymers and copolymers, including all molecular weight and
density ranges and degrees of crosslinking, particularly
polyethylene and polypropylene homopolymers and copolymers; and
ethylene acid copolymers from the copolymerization of ethylene with
acrylic or methacrylic acid or their corresponding acrylate resins.
Materials for the overmolded polymer can also include thermoplastic
elastomers covering a hardness range of from 30 Shore A to 75 Shore
D.
[0082] The combination of the above polymers must satisfy certain
conditions. The plastic conduit must not soften and begin melt flow
to the point where it loses all structural integrity. One of the
keys is the recognition that the plastic conduit must be capable of
maintaining structural integrity during the overmolding conditions
during which the overmolded second polymer is in melt flow. It is
recognized however, that due to the presence of a metallic mandrel
within the internal diameter of the plastic conduit, this concern
is minimized. When using an internally-cooled mandrel, it is
possible to heat the mold to a higher temperature than possible if
the mandrel is not cooled.
[0083] In a preferred embodiment of the invention, the composition
of the overmolded second polymer will be such that it will be
capable of at least some melt fusion with the composition of the
inner polymer conduit, thereby maximizing the leak-proof
characteristics of the interface between the inner polymer conduit
and overmolded second polymer. There are several means by which
this may be effected. One of the simplest procedures is to insure
that at least one component of the inner polymer conduit and that
of the overmolded second polymer is the same. Alternatively, it
would be possible to insure that at least a portion of the polymer
composition of the inner conduit made of the first polymer and that
of the overmolded second polymer is sufficiently similar or
compatible so as to permit the melt fusion or blending or alloying
to occur at least in the interfacial region between the exterior of
the inner polymer conduit and the interior region of the overmolded
second polymer. Another manner in which to state this would be to
indicate that at least a portion of the polymer compositions of the
plastic conduit and the overmolded second polymer are miscible.
[0084] In a preferred embodiment, the flexible position retaining
means would have the physical properties such that it would have
the appropriate strength to retain a nonlinear position when the
final tubing product is manually bent by an external force. The
polymer used to create the inner conduit as well as the overmolded
second polymer will typically have physical properties such that
they will relax back to their original linear position when any
external bending force is released. The flexible wire must have
adequate strength to withstand the relaxation pressure exerted by
the polymer materials upon the release of the external force so the
final tubing product will retain the new nonlinear position.
[0085] In one specific embodiment of this invention which meets the
above criteria, the plastic conduit will be a polypropylene,
polyethylene, or nylon material and the overmolded second polymer
will be the same or similar polypropylene, polyethylene, or nylon
material. The position retaining means will be a metallic wire,
preferably selected from the metals aluminum, copper or steel
(preferably stainless).
[0086] In an alternate embodiment, it is recognized that when the
injection overmolded second polymer is capable of shrinkage upon
cooling, and the end-use application involves only low pressure, a
mechanical shrink-fit may be employed. While in a most preferred
embodiment, a molecular bond will occur between the inner conduit
made of the first polymer and exterior second polymer overmold, in
some applications, where an absolutely leak-proof conduit is not
required, or for applications wherein leakage is not an issue, it
is possible to forego this type of bond in exchange for a
mechanical bond.
[0087] It is foreseen and recognized by this invention that
different combinations of quantities and positions of the wires
allowing the position retention of the tubing can be used. Varying
the location of, the distance between, the percentage of insertion
of, and the length of the wire(s) along the length of the tubing
will allow many alternative retention strengths and ability to
position the final tubing product. For example, one embodiment may
require two flexible wires down the total longitudinal length of
the tubing on opposite sides of the tube, while another embodiment
may require four flexible wires on each quarter of the final tubing
product down alternating upper and lower longitudinal halves. There
is an infinite number of combinations and positions of the flexible
wires in the final tubing product. The combination of quantity and
position of the flexible wires appropriate for the desired
application will depend on the design characteristics of the final
tubing product, such as degree of bend desired, strength of bend
desired, etc. Typically, the more wires used, the greater length of
the wire inserted or embedded, and the closer the wire spacing is
the stronger the position retention of the final tubing product
will be.
[0088] A hollow conduit, being primarily round, or having n sides
wherein n is greater than or equal to three is described herein.
The hollow conduit is comprised of a polymer inner conduit having a
pair of opposed ends and an interior and exterior surface. An
overmolded corrugated polymer is bonded between at least a portion
of the ends and at least a portion of the exterior surface of the
inner conduit. The overmolded polymer has at least one flexible
position retaining means at least partially embedded within. The
flexible position retaining means within the overmolded polymer may
be a metallic wire. The inner conduit may be a thermoset, and the
overmolded corrugated plastic may be a thermoplastic.
[0089] A process of creating above mentioned hollow conduit
comprises of extruding a first polymer conduit, cutting said
conduit to a pre-determined length, and inserting the length into a
split mold having a cavity defined therein. At least one flexible
position retaining means is inserted into said mold, and at least
one second polymer is injection molded onto the plastic conduit and
at least partially onto the position retaining means to form a
position retaining tube. The mold is then opened and the position
retaining tube is removed. The flexible position retaining means is
a metallic wire. The first polymer conduit may be a thermoset, and
the second polymer may be a thermoplastic. The cavity in the mold
may be corrugated.
[0090] This invention has been described in detail with reference
to specific embodiments thereof, including the respective best
modes for carrying out each embodiment. It shall be understood that
these illustrations are by way of example and not by way of
limitation.
* * * * *